PTP500 inside a roof space

Hi

Has anyone enjoyed much success installing PTP500/300 systems inside pitched roof spaces? This is something we have been trying out for listed buildings in the UK with some interesting results. LQ is very good so long as the link is LOS (apart from the roof!) up to around 8-900m. So far we have only tried this under old slate pitched roofs, typically found on listed buildings. Any other feedback would be appreciated!